The present invention generally relates to vertical power components. It more specifically relates to the provision of a voltage linked to the anode voltage of such a component.
Generally, in vertical power components, the rear surface is uniformly metallized and corresponds to the anode of the component, while the front surface comprises a cathode metallization and one or several control terminals. Generally, the anode is brought to a high voltage and it may be useful to have a detection voltage varying in the same way as the anode voltage.
FIGS. 1A to 5A show simplified cross-section views of various examples of vertical power components of cellular type. FIGS. 1B to 5B show equivalent diagrams. In all cases, it is considered that the structure is formed from a lightly-doped N-type substrate 1.
FIG. 1A shows a cross-section view of a cell of a cellular-type thyristor. On the rear surface side of substrate 1 is formed a P-type layer 2 corresponding to the anode layer and coated with an anode metallization MA. On the front surface side is formed a P-type well 3, in which are formed heavily-doped N-type cathode regions 4. Preferably, the central portion of each well comprises a heavily-doped P-type region 6. A cathode metallization MK is integral with regions 4 and 6 and a gate metallization G is integral with well 3.
FIG. 1B shows the conventional equivalent diagram of a thyristor formed of the association of two PNP and NPN transistors. In FIG. 1B as in FIGS. 2B to 5B, the anode is shown at the top of the drawing, while in the cross-section views of FIGS. 1A to 5A, the anode is shown at the bottom of the drawing.
FIG. 2A shows a cross-section view of vertical MOS transistors or of an IGBT transistor. In the case of a MOS-type transistor, rear surface layer 2 is of type N+. In the case of an IGBT transistor, rear surface layer 2 is of type P+. The structure diffused on the front surface side is similar to that of a cellular thyristor and comprises a P-type well 3, an N+-type region 4, and a P+-type region 6. Cathode metallization MK is similar to that of FIG. 1A. The control electrode corresponds to a gate metallization G isolated from the periphery of well 3 and formed thereabove. FIG. 2B shows the equivalent diagram in the case where layer 2 is of type P+, that is, where the component is an IGBT transistor. This structure comprises the association of a PNP transistor and of an enrichment MOS transistor connected between the base and the collector of the PNP transistor.
FIGS. 3A and 3B show a gate turn-on and turn-off MOS thyristor.
FIGS. 4A and 4B show a structure of an emitter-switched thyristor, currently called an EST structure.
FIGS. 5A and 5B show a cross-section view of a base-resistor thyristor, currently designated as a BRT.
FIGS. 3 to 5 will not be described in more detail, and it should only be noted that a P+-type layer 2 coated with an anode metallization MA is provided on the rear surface side. To simplify the understanding of these structures, the gates of the MOS transistors implied in FIGS. 3A, 4A and 5A have been designated as G1 and G2, and these gates have been designated in the same way in the equivalent diagrams of the corresponding FIGS. 3B, 4B, and 5B. For further details, reference can be made to xe2x80x9cTrends in Power Semiconductor Devicesxe2x80x9d, B. J. Baliga, IEEE Transactions on Electron Devices, vol. 43, October 1996, pp. 1717-1731.
FIGS. 1 to 5 have only been described to remind the structure of a few examples of vertical components to which the present invention is likely to apply.
The object of the present invention is to provide a voltage sensor likely to provide, on a front surface electrode of the component, a voltage much lower than the anode voltage, but varying in the same direction as this anode voltage. In other words, a voltage which is the image of the anode voltage is desired to be obtained.
To achieve this object, the present invention provides a sensor of an anode voltage of vertical power component selected from the group comprising the so-called thyristor, MOS, IGBT, PMCT, EST, BRT transistor, MOS thyristor, gate turn-off MOS thyristor, formed in a lightly-doped N-type substrate and having its rear surface, coated with a metallization, which corresponds to the anode of the component, comprising, on the front surface side, an area of the substrate surrounded at least partially with a P-type region at a low voltage as compared to an anode voltage, said area being coated with a metallization in ohmic contact therewith, on which is provided an image of the anode voltage.
According to an embodiment of the present invention, the metallization is formed on a heavily-doped N-type region.
According to an embodiment of the present invention, the anode metallization is formed on a P+-type region.
Further, the present invention aims at a specific use of such a sensor to detect whether the load connected to the power component is in short-circuit.
The present invention also provides a use of the above-mentioned anode voltage sensor to inhibit the operation of a vertical power component when the detected voltage exceeds a predetermined threshold.
The present invention also provides a circuit for controlling the turning-off of a vertical power component comprising a voltage sensor such as mentioned hereabove, the output voltage of which is applied to the control terminal of a switch connected between the cathode and the control terminal of a vertical power component that can be turned off when this control terminal is connected to the cathode, a delay circuit being interposed between the sensor voltage and the gate terminal.
According to an embodiment of the present invention, the delay circuit comprises a MOS transistor, the gate of which receives the signal from the sensor and the main circuit of which is connected between the gate of said switch and a resistor connected to the control terminal of the vertical component.